Me in IT UNIX/Linux Consultancy is based in Breukelen, The Netherlands and specialized in UNIX and Linux consultancy. Experience with Red Hat Enterprise Linux (Red Hat Certified Architect), Fedora Project, CentOS, OpenBSD and related released Open Source products makes Me in IT UNIX/Linux Consultancy a great partner in implementing, maintaining and upgrading your environment.
Open Source software is an important aspect of any Linux distribution. Me in IT UNIX/Linux Consultancy tries to use Open Source software where possible and tries to share experiences actively. In the articles section you will find many UNIX/Linux adventures shared for others to benefit.
So you have a user (or a group of users) on you Linux machine and want them to be able to execute something specific that normally can only be done by root or some other privileged user? Use sudo to solve your problem.
Open the sudoers file using visudo.
Append this line:
%groupname ALL= NOPASSWD: /your/command -o with -o options -o and arguments like this
This will enable the group "groupname" to execute "/your/command", only with the specified options and arguments. The NOPASSWD makes sudo not ask for a password. Now the user can type:
$ sudo /your/command -o with -o options -o and arguments like this
Here is a trick to speedup your login to servers. This nice trick only works when you login to a box for the second time, now you might stop reading, but actually logging in again on a box occurs frequently on an average day with me.
First, lets measure time without any changes to SSH.
$ time ssh host ":"
Now let's modify ~/.ssh/config with these lines on top:
And measure again:
$ ssh host ":"
$ time ssh host ":"
Wow, that is an improvement of more than 14 times! Be aware this does not speed up SSH, it only speeds up the login process, but, always good to see speed improvements. Also be aware that your first SSH connection to a certain box will not be faster, only "recycled" connections (second or more times) are faster.
Here is a (very) extensive article about using SSH tunnels to punch through firewalls. Well written and clear!
Setting up a network interface, it's routes, resolving and so on, can be complicated when you don't know your way around in OpenBSD. You will see it's not difficult at all to setup or change the network configuration of a box when you know about the existence of these files and man-pages.
Well, you should be able to configure the network cards on your OpenBSD machine now.
Sometimes you will find additional configuration in /etc/rc.local, like an extra route to you VPN network. OpenBSD does not facilitate for these extra parameters, so adding them to /etc/rc.local is a good, but not very generic option.
The command cd, which can change directory, seems as the most simple command there is. Guess what; there are a few tricks you can use to navigate faster over a filesystem.
|cd||Go to the home directory.|
|cd -||Go back to the previous directory.|
|cd -P /directory||Go to the physical directory, so translate all symbolic links to what they point to.|
|cd -L /directory||Go to that /directory and do follow symbolic links. This is default behaviour.|
Here is a demonstration about that -P and -L behaviour:
$ cd /tmp ; mkdir test
$ ln -s test symlink
$ cd symlink ; pwd
$ cd -P ../symlink ; pwd
Here is a small script to find files with the name "access_log" or "error_log" which are larger then 1 megabyte. It rotates file to .1, .2, .3, etc.
for type in access_log error_log ; do
find /var/www/virtualhosts/*/logs -size +1024k -a -name $type | while read file ; do
for number in 9 8 7 6 5 4 3 2 ; do
if [ -f $file.$number ] ; then
mv $file.$(($number-1)) $file.$number
mv $file $file.1 && touch /tmp/moved
if [ -f /tmp/moved ] ; then
Since a year or so my interest has been raised for small devices (a bit like appliances) that are capable of running Linux or OpenBSD. I used to have a Soekris 4801, but after lightning struck it, I had to throw it away.
Since that lightning, I have seen these devices that seem capable of replacing the Soekris 4801, not very ease as the Soekris 4801 had three network ports, a serial port, a casing around it, a USB port and an Compact Flash slot. Here are some alternatives:
The PC Engines ALIX 2c3 seems to be the best alternative for a reasonable price. Let go for it, I'll let you know how it worked out.
Looks great, the black page actually saves energy. Not alot of things to see, just 2 links: About Cuil and Your Privacy.
In the "About" section Cuil claims they are the biggest search engine. How could that be?
The search results are neatly presented, looks great!
At a first glance; perfect! When searching for a PXE problem I experienced lately the results are disappointing. No relevant results found.
When searching for my own name, it presents me a "Explore by Category" box, about "Field Marshals Of Nazi Germany"! Come on, that's not closely correct. In fact; on the first page is displays 11 suggestions, only 4 are relevant. (36%) Google show 10 results, 8 are relevant. (80%)
So; looks great, but displays irrelevant information.
Difficult to tell, as the search engine is not very old, but there is some pretty new information to be found.
So; my guess: pretty good, just as Google.
Looks promising, not very accurate at the moment. I will be keeping an eye to this search engine, could be that it will be more accurate in the near future.
Here are some UNIX/Linux commands that have really long man pages.
By the way, technically you will find the biggest man page (in bytes) with this command:
$ find /usr/share/man/ -type f -ls | sort -k 7 -r -n | head -n 10
tcpdump -i eht0 udp dst port 53
ulimit -awill help you.
Manpages are absolutely required. Some software projects considder a missing man page a bug. They are quite right.
I see many colleagues using ping to test if a machine is up. Ping does not tell you if a machine is up, it send an ICMP echo request to a machine and might receive an ICMP echo reply.
Besides that, many people use ping to check the IP address of a machine. Use nslookup, or even better; use host. Those tools are designed to find out a the IP address of a hostname. (or the other way around.)
Here is why you should not use ping to test a machines availability.